The susceptibility of several cell lines from different animal origins to cytotoxic induction by reoviruses was examined. The following groups of cells were found to be susceptible: certain tumor and spontaneously established cell lines of human origin and certain established cell lines of murine origin. In contrast, the following cells were found to be insusceptible: human diploid cell lines, primary and established cells of subhuman primates, primary and virally transformed murine cells, normal rat kidney cells, and baby hamster kidney cells. With rare exceptions susceptibility to CT-induction could be related to agglutinability with concanavalin A. In contrast, no such relationship could be established on the basis of adsorption kinetic studies of the virus.